1. Field of the Invention
The present invention relates to a modified polyolefin composition and to a process for producing the same. Particularly, the present invention relates to a modified polyolefin composition having an excellent bonding property and being useful for producing shaped articles having an excellent impact resistance, especially at a low temperature, and to a process for producing the same.
2. Prior Art
It is known that crystalline polypropylene is useful for producing various shaped articles, for example, injection-molded articles, films, and injection-blow molded articles, for example, bottles, which must exhibit excellent physical properties, for example, rigidity and resistance to thermal deformation.
It is also known, however, that since the molecules of the crystalline polypropylene have no polar groups, the crytalline polypropylene exhibits an extremely poor bonding activity to synthetic resin articles, metal articles, and wood articles.
There have been attempted various methods for the purpose of enhancing the bonding property of the crystalline polypropylene. In the attempts, a surface of a crystalline polypropylene article to be bonded to another article was treated with a flame, a corona discharge, or a solvent. These attempts were not always successful in enhancing the bonding property of the crystalline polypropylene.
In another attempt, a crystalline polypropylene was subjected to an addition reaction with an unsaturated dicarboxylic acid, for example, maleic acid, or its anhydride, in the presence of a radical reaction initiator at an elevated temperature so as to modify the crystalline polypropylene to a modified polypropylene having functional radicals which are effective for enhancing the bonding property of the crystalline polypropylene. This attempt was, however, not successful because the bonding property of the resultant modified polypropylene was unsatisfactory. Also, the resultant modified polypropylene exhibited a poor impact resistance at a low temperature.
In still another attempt, Japanese Unexamined Patent Publication No. 52-8035 discloses a process for producing a polyolefin composition usable as a coating material. In this process, a mixture of a crystalline polyolefin, an unsaturated aliphatic carboxylic acid or its anhydride, and a rubber compound was heated at a temperature higher than the melting point of the crystalline polyolefin. However, the bonding property and impact resistance of the modified polyolefin composition at a low temperature were still unsatisfactory.